At present, structures for foundations of offshore wind turbine generators usually employ grouted connections. For example, for a mono-pile foundation, a tower is connected with a pile via a grouted connection; for a tripod foundation and jacket foundation, a jacket is connected with piles via a grouted connection between pile sleeves and piles.
In practical implementation, performance of grouted connections can be improved by enhancing the strength of the grouting material and improving grouting techniques, and structural designs of grouted connections also play an important role. The roughness of pipe walls impacts the friction between the pipe and the grout; shear keys may enhance mechanical bond forces. However, all these stress modes are passive. Therefore, it is desired to enhance the bearing capacity of grouted connections by means of active holding actions of pre-stresses.